As is well known, a cylinder includes therein a piston that undergoes sliding movement in a piston slide hole that is formed in a tube, and a piston rod connected to the piston and which is displaced integrally with the piston upon the piston making advancing and retracting movements. In this type of cylinder, for example, a predetermined workpiece is attached to the piston rod. In this case, the workpiece undergoes movement accompanying displacement of the piston rod. In other words, the cylinder functions as a transport means for transporting the workpiece.
Incidentally, in such a cylinder, due to dimensional variations, a gap tends to develop between both members of the piston and the piston slide hole. Therefore, when a load (hereinafter referred to as a “lateral load”) in a direction perpendicular to the axial direction is applied with respect to a distal end of the piston rod that is exposed from the piston slide hole, another end part of the piston rod on a side thereof that is inserted into the piston slide hole is displaced in a direction opposite to the direction of the lateral load. More specifically, when the piston rod and the piston are displaced, they tend to become inclined easily, and it is likely for looseness or so-called rattling of the piston rod to occur.
Thus, it has widely been practiced to provide a guide mechanism in order to prevent such looseness or rattling of the piston rod. For example, as shown in FIG. 1 of Japanese Laid-Open Patent Publication No. 2006-105391, in a guide mechanism equipped cylinder, one piston slide hole, and two guide holes sandwiching the piston slide hole therebetween are formed in a tube. A piston rod that is inserted into the piston slide hole, and guide rods that are inserted into the respective guide holes are connected respectively to a connecting plate. Therefore, the guide rods and the plate also undergo displacement in following relation to the advancing and retracting operations of the piston rod.
In this configuration, since the piston rod is connected to the guide rods through the connecting plate, it is unlikely for rattling to occur even if lateral loads are applied. Further, since it is remarkably difficult for the piston rod to undergo rotation, non-rotational precision also is enhanced.
As shown in FIG. 3 of Japanese Laid-Open Patent Publication No. 09-303318, in the same manner as in Japanese Laid-Open Patent Publication No. 2006-105391, a guide mechanism equipped cylinder is disclosed, which includes one piston rod, and two guide rods that are arranged so as to sandwich the piston rod therebetween.